Fallen trees and tree silhouettes

January 11, 2017

This morning I locked my bike up at parking lot 10, on the southeast edge of the road going around the East Woods. The woods there are dominated by large old trees, all silhouettes an hour before dawn. I was hoping to find a tree that I heard fall as I was biking out last night. I had left at about 4:30, and the wind was ferocious. Somewhere between P10 and P8, I believe, I had heard the unforgettable sound of a great tree cracking and then falling through the woods, crashing through other trees on its way down. I’ve only once seen a tree of this size go down, in a red oak woods in Madison about 20 years ago. It had been the same sound: a substantial crack that could only be from something very large breaking. The sound was riveting, and I looked around rapidly to see if I was in the way… I had no idea where the sound had come from, but it was close. Then I saw the tree about 30 feet away, falling downhill parallel to the trail I was on. It fell like a dancer falls, arched legs and back and arms, until she catches herself in a short run. But of course the oak kept falling, knocking through maple saplings and scraping the bark off nearby trees until it hit the ground and bounced, slowly, as a massive body must. The tree had broken off perhaps 15 feet above the base, and the wood was wet and ragged, twisted in the places where it was still attached. The bark sloughed off like soaked flannel, sagging and buckled at the edges. The ground around the tree was remarkably undisturbed: wildflowers and sedges and leaf litter was mostly intact, with only occasional broken spots where a branch had punctured the ground. The bark on the trees the falling oak had struck was scraped off cleanly, and the exposed wood was fresh and white. Since then, I have felt that every fallen tree in the woods is a near-miss at watching another tree go down. I hope to see such a thing once more before I go.

At the top of the hill just south of P10, the oaks all appeared to be forest-grown, not a lot of knobs of lower branches broken off after decades of growing in the sun. There were branches on the ground, some large enough to trip you if you weren’t paying attention, but no large trees across the path, and nothing newly fallen of any size that I could see in the woods around me. Walking down the hill, the white oaks increasingly pick up short, skinny lower branches, decorated with marcescent leaves. Tree after tree showed this pattern: a naked crown and young branches that had retained their leaves after the life was out of them. This is not uncommon in oaks, and it stands out better at night. Why do the trees do this? Is there some advantage to trees that exhibit marcescence? And why the younger branches, unless marcescence is just a developmental side-effect, a failure to get all the way to the abscission layer in the fall. There may be nothing deliberate about it: it may be a textural artifact on an otherwise functional tree, no more functional than thinking wrinkles.

At the bottom of the hill, just east of parking lot 8, the woods open to the south, grading from forest to savanna to wet meadow. I picked my way through to the edge of the Phragmites and reed-canary grass meadow, then walked to P10 and crossed the road. I grew restless and turned on my flashlight, exploring initially for sedges. Hunting for sedges is my go-to activity outside, and it’s reliable fun in almost any season. I found Carex blanda and C. albursina, and a whole mess of something I should know but couldn’t put my finger on. I know there should be flocks of C. hirtifolia out there, but I didn’t see any. It may be that this is one of the odd woodland sedges that is not semi-evergreen. There’s work to be done on this.

I prowled and scanned on the forest floor and was having a great time out there in the dark, when I suddenly realized the tree I was looking around was a cottonwood in the middle of the oak forest. I turned off my light and looked at the bark, turned it back on and searched for cottonwood leaves among the white oak and sugar maple litter at the base of the tree, looked for the great buds on the branch tips above. Why was I surprised by the cottonwood? Should I be? I’m always unduly influenced by my own typically too-narrow experience of plants. Jason Sturner collected a cottonwood specimen northwest of the Big Rock Visitor Station in 2007, and presumably there are scattered cottonwoods elsewhere in the forest. I’ve just not noticed them, or I’ve noticed them and not given them enough thought to remember having seen them. This tree was perhaps 2½ feet in diameter, which is not particularly large for the fast-growing cottonwood. I gather that it established in the shade under the oaks. I have something else to keep a watch for this year.

On my walk out, I my full attention to the standing trees, and I was now all the more happy to have the flashlight with me. I kicked around among the white oaks, the red oaks, the sugar maples, studying silhouettes in the dark and bark by flashlight. The old maples seem to have branches that diverge more near the crown than the oaks of the same height and diameter. I worked my way back to the easternmost edge of the woods, came up to the road from the forest side. There was a fallen hop-hornbeam, quite old, but no big trees. There was the stump of an oak that must have fallen over a decade ago, sawed off to get the trunk off of the road, but nothing newly fallen.

Wherever that big old tree was, I didn’t run across it. Dawn was coming on by the time I got back to my bike, and I left my light off as I biked through the clearing towards work.


Addendum, 4:30 p.m. On the bike-ride out later that day, I found what I suspect is the tree I had heard snap off in the wind. It was to the north of the road, not to the south, a white ash riddled with fungus, ca. 1.5 ft dbh, broken off about 6′ above the base.

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